He’s yet another populist politician
Yes, he campaigned for the role on the basis that he would use a populist but not nationalist approach. The membership figures, and the election results both show that his approach has moved the party from what many saw as a campaign group (a survey somewhere showed that too many people muddled Greenpeace with the Green Party, and wondered why a global environmental charity were campaigning for parliament in the UK. That position has more or less been corrected.
going against a lot of (in this case) Green traditional policies.
Examples? As leader he would quickly be called to account by the part if this is the case. The GP has always allowed prospective parliamentary candidates to hold an opinion that does not align with the membership opinion. The requirement is that they must state the party position, their own position, and the reason for any difference in opinion. Wouldn't you favour that that for all politicians in all parties?
You can’t change anything if you are not in power, fine.
Not acually true, but it does become true when people are denied their fundamental rights to speak truth to power, and to protest - rights that have been reduced by recent governments of both stripes.
But you can’t be trusted either.
He has exaggerated, just as the claims against him are exaggerated and being made out by you.
Part of Zack's failure is to apologise rather than resist the lies and exaggerations made out against him, such as this boob whisperer nonsense.